Americans' Heads Are Getting Bigger

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The skull size of white Americans has increased 6.8 percent since the late 1800's, according to research performed by forensic anthropologists at the University of Tennessee at its main campus in Knoxville.

Researchers at the university's Forensic Anthropology Center studied 1,500 skulls of men and women of European descent dating back from the mid 1800's and found that male skull sizes have increased by 200 cubic centimeters, roughly the size of a tennis ball. Women's skulls have increased by 180 cubic centimeters, the study reports.

So we know that our heads have gotten larger, but why? It's hard to pinpoint according to Richard Jantz, a professor emeritus at UT and one of the three anthropologists who performed the study. "We had hypotheses, but it's difficult to test," Jantz told Business Insider. "It's so multidimensional that it's hard to say what specific aspect is influencing skull size."

Jantz said that the unique environment we live in has likely caused many changes in the human body, including an increase in height in addition to skull size. We've never had this level of nutrition in a society before, Jantz said, which is one of the several factors that has to be taken into account.

Other causes of our bigger heads include improved medical care, the decrease in infant mortality and a decrease in the calories we expend as a society, Jantz added. "All of this is happening simultaneously," Jantz said, which is why it's really so hard to pin the skull growth on just one factor.

Jantz said there isn't the data in other countries to determine whether other regions and ethnicities have encountered similar skull growth, but he said that it was likely they have larger heads too than they did just 150-200 years ago.